The Switch "seems" (we haven't seen everything yet) like it does everything, just nothing "great" which would be a mediocre device to home console fans and portable fans.
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My core concern is the "jack of all trades, do nothing great, do nothing bad" aspect of what I'm seeing as of right now
I don't see how the Switch would be a mediocre handheld. As a home console, I get it, it's less powerful than the competition. As a handheld though, there's nothing mediocre about it. You mentioned the battery life, but we have no idea what the battery life is. Dev kits are not the same as retail products. We also don't know what it was running anyway nor what the battery life in sleep mode is like. I'm not expecting miracles, but the 3DS was already 3-5 hours, so I get the impression that they're shooting for something in that range, though I think it could last longer than the 3DS in sleep mode since it's bigger.
If you think it's too big, well, knowing Nintendo you'll eventually get a revision with a different screen size. I think they were right, though. The N3DS and N3DS XL were released on the same date and the XL has been considerably more popular. The regular XL has been outselling the regular 3DS since it came out. The vast majority of people don't expect to be able to carry a dedicated handheld in their pocket. Their phone, yes, because they need it on them always, but a gaming system, they want a bigger screen, especially if the graphics are detailed and in HD. People are used to bigger screens nowadays. TV screens are bigger, phone screens are bigger, tablets are very popular. They made the choice that they thought would please the most people and I think they're correct in their assessment, so I don't think the large screen size will work against it. I think it will be seen as a good thing.
It's a giant leap from the 3DS - and a significant leap from the Vita - in resolution and power, it has two analog sticks, local multiplayer out of the box and it's pretty obvious that they will sell different types of Joy-Cons, so the handheld will most likely be more customizable than the 3DS and the Vita. I doubt the apparent lack of a camera will bother many people.
And, obviously, as a primarily handheld gamer, I've still sometimes been curious to see what the games would look like on a TV screen, so being able to do so is still a plus even for someone who doesn't intend on using it as a home console much.